Display panel and method of manufacturing thereof

ABSTRACT

A display panel and a method of manufacturing thereof are provided. A hole injection layer, a hole transport layer, a light emitting layer, and a planarization layer are formed by an inkjet-printing method. Specifically, solvents including hole injecting layer material, hole transporting layer material, light emitting layer material, and planarization layer material are evaporated by vacuum drying so as to uniformize the surface of the entire layer, thereby improving light uniformity. Moreover, a notch of the light emitting layer can be effectively filled by disposing a planarization layer on the light emitting layer, so a uniform layer can be formed, which can reduce the current accumulated at the notch. Therefore, the light uniformity of the display panel is improved, and the risk of leakage current at the notch is also reduced.

BACKGROUND OF INVENTION Field of Invention

The present invention relates to the field of display technology, andmore particularly, to a display panel and a method of manufacturingthereof.

Description of Prior Art

Quantum-dot light-emitting diode (QLED) is a self-luminous technologythat does not require a backlight. Due to the solution processingcharacteristics of quantum dots, the quantum dot light emitting layercan be formed by spin-coating, blade-coating, inkjet-printing, etc.Compared with the previous methods, inkjet-printing technology canaccurately deposit quantum dot light emitting materials at appropriatepositions, and uniformly deposit semiconductor materials to form thinfilm layers. Therefore, a utilization rate of materials is very high,which can reduce production cost and simplify fabrication process, andit is expected to achieve mass production. Inkjet-printing technology iscurrently regarded as an effective method to solve the problem oflarge-size QLED screen manufacturing.

The uniformity of the film surface after inkjet-printing is mainlyaffected by the “coffee ring” effect. The uniformity of the film surfacedirectly affects the efficiency and life of the device. Therefore, the“coffee ring” effect should be minimized during the printing process.The quantum dot films formed by inkjet-printing not only faces theproblem of “coffee ring” but also has a high and low undulating shapedue to large volume and easy aggregation. Since the resistance at thelower portion is relatively low, more current flows at a lower portion,so that the lower portion is brighter and the film uniformity is poor.

Therefore, it is urgent to provide a new display panel for solving theproblem of uneven illumination caused by uneven film thickness.

SUMMARY OF INVENTION

It is an object of the present invention to provide a display panel anda method of manufacturing thereof, which can effectively solve theproblem of uneven illumination caused by uneven film thickness.

A display panel includes: a substrate and an organic functional layerdisposed on the substrate and surrounded by a pixel defining layer. Theorganic functional layer includes: a first electrode disposed on thesubstrate; a hole injection layer disposed on a side of the firstelectrode away from the organic functional layer; a hole transport layerdisposed on a side of the hole injection layer away from the firstelectrode; a light emitting layer disposed on a side of the holetransport layer away from the hole injection layer; a planarizationlayer disposed on a side of the light emitting layer away from the holetransport layer; an electron transport layer disposed on a side of theplanarization layer away from the light emitting layer; an electroninjection layer disposed on a side of the electron transport layer awayfrom the planarization layer; and a second electrode disposed on a sideof the electron injection layer away from the electron transport layer.At least one notch is formed on a side of the light emitting layerattached to the planarization layer, at least one protrusion is formedon a side of the planarization layer attached to the light emittinglayer, and the at least one protrusion is correspondingly fitted withthe at least one notch.

In one embodiment, the at least one notch is continuously distributed onthe light emitting layer, and the at least one protrusion iscontinuously distributed on a side of the planarization layer close tothe light emitting layer.

In one embodiment, a thickness of the planarization is 5 nm to 20 nm.

In one embodiment, material of the planarization layer comprisespolymethyl methacrylate, polyvinylpyrrolidone, and polystyrene.

In one embodiment, the planarization layer and the electron transportlayer are made of a same material.

In one embodiment, the light emitting layer comprises a plurality ofquantum dots.

A method of manufacturing a display panel includes following steps:providing a substrate, and the substrate includes a functional region;forming a pixel defining layer on the substrate, and the pixel defininglayer surrounds the functional region; forming a first electrode on thefunctional region, and the first electrode is attached to the substrate;injecting a hole injecting material ink onto the first electrode, vacuumdrying to remove a hole injecting material ink solvent, and baking toform a hole injection layer; injecting a hole transporting material inkonto the hole injection layer, and vacuum drying to remove a holetransporting material ink solvent, and baking to form a hole transportlayer; injecting a quantum dot light emitting material ink onto the holetransport layer, and vacuum drying to remove a quantum dot lightemitting material ink solvent, and baking to form a light emittinglayer; injecting a planarization layer material ink onto the lightemitting layer, and vacuum drying to remove a planarization layermaterial ink solvent, and baking to form a planarization layer; formingan electron transport layer on the planarization layer; forming anelectron injection layer on the electron transport layer; and forming asecond electrode on the electron injection layer.

In one embodiment, the step of forming an electron transport layer onthe planarization layer is performed by evaporation, and the step offorming an electron injection layer on the electron transport layer isperformed by evaporation.

In one embodiment, the step of forming an electron transport layer onthe planarization layer is performed by inkjet-printing, and includesinjecting an electron transport layer material ink onto the lightemitting layer, vacuum drying to remove an electron transport layermaterial ink solvent, and baking to form the electron transport layer.

In one embodiment, the step of forming an electron injection layer onthe electron transport layer is performed by inkjet-printing, andincludes injecting an electron injection layer material ink onto theelectron transport layer, vacuum drying to remove an electron injectionlayer material ink solvent, and baking to form the electron injectionlayer.

A display panel and a method of manufacturing thereof are provided. Ahole injection layer, a hole transport layer, a light emitting layer,and a planarization layer are formed by an inkjet-printing method.Specifically, solvents including hole injecting layer material, holetransporting layer material, light emitting layer material, andplanarization layer material are evaporated by vacuum drying so as touniformize the surface of the entire layer, thereby improving lightuniformity. Moreover, a notch of the light emitting layer can beeffectively filled by disposing a planarization layer on the lightemitting layer, so a uniform layer can be formed, which can reduce thecurrent accumulated at the notch. Therefore, the light uniformity of thedisplay panel is improved, and the risk of leakage current at the notchis also reduced.

BRIEF DESCRIPTION OF DRAWINGS

In order to more clearly illustrate the technical solutions in theembodiments, the drawings described in the description of theembodiments are briefly described below. It is obvious that the drawingsin the following description are only some embodiments of the presentinvention. Other drawings can also be obtained from those skilledpersons in the art based on drawings without any creative effort.

FIG. 1 is a schematic structural view of a display panel according toone embodiment the present invention.

FIG. 2 is a partial structural schematic view of the display panelaccording to one embodiment of the present invention.

REFERENCE NUMERALS

display panel 100; substrate 101; organic functional layer 102; holelayer 103; first electrode 1021; hole injection layer 1022; holetransport layer 1023; light emitting layer 1024; planarization layer1025; electron transport layer 1026; electron injection layer 1027;second electrode 1028; functional area 130; notch 110; and protrusion120.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following description of the various embodiments is provided withreference to the accompanying drawings. The directional terms mentionedin the present invention, such as “upper,” “lower,” “front,” “back,”“left,” “right,” “inside,” “outside,” “side,” etc., are merely indicatedthe direction of the drawings. The names of the elements mentioned inthe present invention, such as the first, second, etc., are onlydistinguishing between different components and can be better expressed.In the drawings, structurally similar elements are indicated by the samereference numerals.

Embodiments of the present invention are described in detail herein withreference to the drawings. The present invention may be embodied in manydifferent forms and the invention is not to be construed as beinglimited to the specific embodiments set forth herein. The embodiments ofthe present invention are provided to explain the practical applicationso that those skilled persons in the art can understand variousembodiments of the present invention and various modifications suitablefor the particular intended application.

Referring to FIG. 1 , a quantum dot light emitting diode device 100 isprovided and includes a substrate 101, a first electrode 102, a holelayer 103, an electron transport layer 104, a quantum dot layer 105, anda second electrode 106.

The substrate 101 is a flexible substrate for supporting the entirequantum dot light emitting diode device. The material of the substrate101 is polyimide; the polyimide material has flexible properties afterdrying.

The first electrode 102 is disposed on the substrate 101. The firstelectrode 102 is a transparent indium tin oxide (ITO) electrode, thatis, an anode.

When the quantum dot light emitting diode device is applied to current,electrons are removed at the first electrode 102, that is, the number of“holes” is increased.

The hole layer 103 is vertically disposed on the first electrode 102,and the hole layer 103 has a sidewall. The hole layer 103 is made of aplurality of carbon nanotubes, and can be obtained by ion vapordeposition. The carbon nanotubes replace conventional hole injectionlayer and hole transport layer as a new hole layer 103, which transportsholes to the quantum dot layer 105.

The carbon nanotubes have good stability, so the holes can beefficiently transported to the quantum dot layer 105, and the number ofholes and electrons can be balanced.

A length of a single carbon nanotube is 1-5 μm, preferably 3 μm, and itmay also be 2 μm or 4 μm. A diameter of a single carbon nanotube is 10to 50 nm, preferably 30 nm, and it may also be 20 nm or 40 nm. (see FIG.3 ).

The electron transport layer 104 is disposed on the sidewall fortransmitting electrons from the cathode. The electron transport layer104 includes at least one high density zinc oxide nanowire for enhancinglight emitting (see FIG. 3 ). The zinc oxide nanowires are obtained bygrowing zinc oxide seeds under water-soluble conditions.

A length of single zinc oxide nanowire is 1 to 5 μm, preferably 3 μm,and it may also be 2 μm or 4 μm. A diameter of the zinc oxide nanowireis 10 to 80 nm, preferably 40 nm, and it may also be 20 nm, 30 nm, 50nm, or 60 nm. (see FIG. 3 ).

The quantum dot layer 105 is disposed on the electron transport layer104. The quantum dot layer 105 emits red or green light under the actionof an external electric field.

The quantum dot layer 105 is manufactured by spin-coating,inkjet-printing, or electroplating methods.

Specifically, if the quantum dot is formulated into a quantum dotsolution, the quantum dot solution is spin-coated on the electrontransport layer 104 by a spin coating method, and then it is sintered.The spin coating rate is 1000-4000 rpm/min, preferably 2500 rpm/min, or1500 rpm/min, or 3000 rpm/min. The sintering time is 30-40 seconds, andthe sintering temperature is 100-200 degrees. The excessiveconcentration of the quantum dot solution may cause formation of amultilayer quantum dot film, and if the concentration of the quantum dotsolution is too light, the single layer coverage may not be enough.

If a single layer film is manufactured by inkjet-printing, the quantumdot solution is directly inkjet printed on the electron transport layer104, and then it is dried. The drying temperature is 100 to 200 degrees.

If a single layer film is manufactured by electroplating, theelectroplating voltage ranges from 0 to 100 V. The drying temperatureranges from 100 to 200 degrees.

The spin-coating, inkjet-printing, and electroplating quantum dotsolution manufacturing methods are repeated at least one to five times,that is, one to five layers of quantum dot films are formed.

The concentration of the quantum dot solution is 10-20 mg/mL, preferably15 mg/mL, and it may also be 12 mg/mL or 18 mg/mL.

The quantum dot layer 105 includes at least one quantum dot, and thequantum dot includes a core and an outer shell, and the outer shellcovers the core.

The material of the core includes any one or more combinations ofcadmium sulfide, cadmium selenide, cadmium telluride, lead sulfide, orlead selenide. The material of the outer shell is made of zinc sulfideor zinc selenide.

The second electrode 106 is disposed on the electron transport layer104, and the second electrode 106 is a cathode. When current is appliedto the quantum dot light emitting diode, the cathode injects electronsinto the circuit.

Finally, an electric field is applied to the quantum dot light emittingdiode device 100 to emit red-light or green-light.

The quantum dot light emitting diode device adopts a vertical typecarbon nanotube so as to replaces a conventional hole injection layerand a hole transport layer, and a zinc oxide nanowire is grown on thesidewall of the carbon nanotube and used to be as an electron transportlayer 104, and a surface of the zinc oxide nanowire is covered with thequantum dot layer 105. When holes and electrons are respectivelyinjected from both ends of the carbon nanotubes and zinc oxidenanowires, photons are generated in the quantum dot layer 105. Thus,each of the zinc oxide nanowires can be regarded as one light emittingunit.

A method of manufacturing a quantum dot light emitting diode device isfurther provided, and the method includes following steps S1 to S7.

Step S1, a substrate 101 is provided. The substrate 101 is a flexiblesubstrate for supporting the entire quantum dot light emitting diode.The material of the substrate 101 is polyimide, and the polyimide has aflexible property after drying.

Step S2, a first electrode 102 is formed on the substrate 101, and thefirst electrode 102 is a transparent indium tin oxide (ITO) electrode,that is, an anode.

When the quantum dot light emitting diode is applied to current,electrons are removed at the first electrode 102, that is, the number of“holes” is increased.

Step S3, at least one carbon nanotube is deposited on the firstelectrode 102 so as to form a hole layer 103, and it is sintered under anitrogen atmosphere for 20 minutes, and the sintering temperature is 150degrees. The hole layer 103 has a sidewall.

A length of a single carbon nanotube is 1-5 μm, preferably 3 μm, and itmay also be 2 μm or 4 μm. A diameter of a single carbon nanotube is 10to 50 nm, preferably 30 nm, and it may also be 20 nm or 40 nm.

Step S4, zinc oxide seed is sputtered on the sidewall of the hole layer103, and it is heated to grow zinc oxide nanowires, and an electrontransport layer 104 is formed. The heating temperature is 95° C.

A length of single zinc oxide nanowire is 1 to 5 μm, preferably 3 μm,and it may also be 2 μm or 4 μm. A diameter of the zinc oxide nanowireis 10 to 80 nm, preferably 40 nm, and it may also be 20 nm, 30 nm, 50nm, or 60 nm.

Step S5, a quantum dot solution is prepared. The concentration of thequantum dot solution is 10-20 mg/mL, preferably 15 mg/mL, and it mayalso be 12 mg/mL or 18 mg/mL.

In the step of preparing a quantum dot solution, the step includesdissolving the first quantum dot solution in a non-polar solvent. Thenon-polar solvent is any one of n-hexane, n-octane, cyclohexane,toluene, and trichloromethane.

The concentration of the first quantum dot solution is 10-30 mg/mL.

Step S6, the quantum dot solution is coated on the zinc oxide nanowireand sintered to form a quantum dot layer 105.

In the step of applying the quantum dot solution to the zinc oxidenanowire, the quantum dot solution is coated for one to five times.

Specifically, if the quantum dot is formulated into a quantum dotsolution, the quantum dot solution is spin-coated on the electrontransport layer 104 by a spin coating method, and then it is dried. Thespin coating rate is 1000-4000 rpm/min. The drying time is 30-40seconds, and the sintering temperature is 100-200 degrees. The excessiveconcentration of the quantum dot solution may cause formation of amultilayer quantum dot film, and if the concentration of the quantum dotsolution is too light, the single layer coverage may not be enough.

If a single layer film is manufactured by inkjet-printing, the quantumdot solution is directly inkjet printed on the electron transport layer104, and then it is dried. The drying temperature is 100 to 200 degrees.

If a single layer film is manufactured by electroplating, theelectroplating voltage ranges from 0 to 100 V. The drying temperatureranges from 100 to 200 degrees.

The spin-coating, inkjet-printing, and electroplating quantum dotsolution manufacturing methods are repeated at least one to five times,that is, one to five layers of quantum dot films are formed.

The quantum dot solution includes a green-light quantum dot solution ora red-light quantum dot solution, and it can be prepared as needed.

Step S7, a second electrode 106 is formed on the electron transportlayer 104. The second electrode 106 is disposed on the electrontransport layer 104, and the second electrode 106 is a cathode. Whencurrent is applied to the quantum dot light emitting diode, the cathodeinjects electrons into the circuit.

Finally, the quantum dot light emitting diode is applied with a voltageof 2.5 V to emit light, and the light is red-light or green-light. Theluminance is greater than 5000 cd/m², and the quantum dot light emittingdiode device 100 has a luminous efficiency greater than 5 cd/A.

The present invention adopts a quantum dot light emitting diode devicewith novel three-dimensional structure. The quantum dot light emittingdiode device adopts a vertical type carbon nanotube so as to replaces aconventional hole injection layer and a hole transport layer, and a zincoxide nanowire is grown on the sidewall of the carbon nanotube and usedto be as an electron transport layer 104, and a surface of the zincoxide nanowire is covered with the quantum dot layer 105.

Referring to FIG. 2 , when holes of the hole layer 103 and electrons ofthe electron transport layer 104 are respectively injected from bothends of the carbon nanotubes and the zinc oxide nanowires, electrons andholes cannot be recombined due to the existence of a heterojunctioninterface. The electrons and holes are transferred to the conductionband and valence band of quantum dots, and the electrons and the holesare combined to generate photons. Thus, each of the zinc oxide nanowiresof the quantum dot layer 105 can be regarded as one light emitting unit.Moreover, one embodiment of the present invention has a relatively highdensity of the zinc oxide nanowires (see FIG. 3 ), which forms a highphotocurrent density, and greatly improves the luminance of the lightand device performance.

In the above, the present application has been described in the abovepreferred embodiments, but the preferred embodiments are not intended tolimit the scope of the invention, and a person skilled in the art maymake various modifications without departing from the spirit and scopeof the application. The scope of the present application is determinedby claims.

What is claimed is:
 1. A display panel, comprising: a substrate; and anorganic functional layer disposed on the substrate and surrounded by apixel defining layer; wherein the organic functional layer comprises: afirst electrode disposed on the substrate; a hole injection layerdisposed on a side of the first electrode away from the organicfunctional layer; a hole transport layer disposed on a side of the holeinjection layer away from the first electrode; a light emitting layerdisposed on a side of the hole transport layer away from the holeinjection layer; a planarization layer disposed on a side of the lightemitting layer away from the hole transport layer; an electron transportlayer disposed on a side of the planarization layer away from the lightemitting layer; an electron injection layer disposed on a side of theelectron transport layer away from the planarization layer; and a secondelectrode disposed on a side of the electron injection layer away fromthe electron transport layer; wherein at least one notch is formed on aside of the light emitting layer attached to the planarization layer, atleast one protrusion is formed on a side of the planarization layerattached to the light emitting layer, and the at least one protrusion iscorrespondingly fitted with the at least one notch.
 2. The display panelaccording to claim 1, wherein the at least one notch is continuouslydistributed on the light emitting layer, and the at least one protrusionis continuously distributed on a side of the planarization layer closeto the light emitting layer.
 3. The display panel according to claim 1,wherein a thickness of the planarization is 5 nm to 20 nm.
 4. Thedisplay panel according to claim 1, wherein material of theplanarization layer comprises polymethyl methacrylate,polyvinylpyrrolidone, and polystyrene.
 5. The display panel according toclaim 1, wherein the planarization layer and the electron transportlayer are made of a same material.
 6. The display panel according toclaim 1, wherein the light emitting layer comprises a plurality ofquantum dots.
 7. A method of manufacturing a display panel, comprisingfollowing steps: providing a substrate, wherein the substrate comprisesa functional region; forming a pixel defining layer on the substrate,wherein the pixel defining layer surrounds the functional region;forming a first electrode on the functional region, wherein the firstelectrode is attached to the substrate; injecting a hole injectingmaterial ink onto the first electrode, vacuum drying to remove a holeinjecting material ink solvent, and baking to form a hole injectionlayer; injecting a hole transporting material ink onto the holeinjection layer, and vacuum drying to remove a hole transportingmaterial ink solvent, and baking to form a hole transport layer;injecting a quantum dot light emitting material ink onto the holetransport layer, and vacuum drying to remove a quantum dot lightemitting material ink solvent, and baking to form a light emittinglayer; injecting a planarization layer material ink onto the lightemitting layer, and vacuum drying to remove a planarization layermaterial ink solvent, and baking to form a planarization layer; formingan electron transport layer on the planarization layer; forming anelectron injection layer on the electron transport layer; and forming asecond electrode on the electron injection layer.
 8. The method ofmanufacturing the display panel according to claim 7, wherein the stepof forming an electron transport layer on the planarization layer isperformed by evaporation, and the step of forming an electron injectionlayer on the electron transport layer is performed by evaporation. 9.The method of manufacturing the display panel according to claim 7,wherein the step of forming an electron transport layer on theplanarization layer is performed by inkjet-printing, and comprisesinjecting an electron transport layer material ink onto the lightemitting layer, vacuum drying to remove an electron transport layermaterial ink solvent, and baking to form the electron transport layer.10. The method of manufacturing the display panel according to claim 8,wherein the step of forming an electron injection layer on the electrontransport layer is performed by inkjet-printing, and comprises injectingan electron injection layer material ink onto the electron transportlayer, vacuum drying to remove an electron injection layer material inksolvent, and baking to form the electron injection layer.